Results from a new European study debunks the common myth that exercise before bed disrupts sleep, with researchers finding that as long as the exercise is not too intense, it can be done at any time of day.
Carried out by researchers from the Institute of Human Movement Sciences and Sport at ETH Zurich, the new analysis looked at 23 eligible studies to assess whether sleep quality can be improved by avoiding physical activity in the hours before bedtime.
The findings, published in Sports Medicine, showed that moderate exercise in the evening did not cause sleep problems in any of the studies examined, even when the training session finished just 30 minutes before bedtime.
The researchers also found that in the night following evening exercise, participants spent 21.2 percent of their sleeping time in deep sleep, whereas following an evening without exercise, they spent an average of 19.9 percent of their shut-eye in deep sleep.
The researchers added that although this difference is small, it is statistically significant. Deep sleep phases are also particularly important for physical recovery.
“If doing sport in the evening has any effect on sleep quality at all, it’s rather a positive effect, albeit only a mild one,” says Christina Spengler, head of the Exercise Physiology Lab at ETH Zurich.
However, one type of exercise did appear to be the exception. The team found that vigorous exercise, such as high-intensity interval training, within an hour before bedtime, may have a negative effect on sleep.
“As a rule of thumb, vigorous training is defined as training in which a person is unable to talk. Moderate training is physical activity of an intensity high enough that a person would no longer be able to sing, but they could speak,” Spengler explained.
Participants who had completed intensive training before bedtime took longer to fall asleep, with the researchers finding that they went to bed with their hearts still beating more than 20 beats per minute faster than their resting heart rate due to not having enough time to recover.
“Vigorous training or competitions should be scheduled earlier in the day, if possible,” added Jan Stutz, lead author of the analysis.
The researchers noted that the findings are a preliminary observation in this area, but concluded that when it comes to wondering what is the best time of day to work out, people should not hesitate to schedule it in the evening. “The data shows that moderate exercise in the evening is no problem at all,” said Stutz.
However, he added: “Not everyone reacts to exercise in the same way, and people should keep listening to their bodies. If they notice they are having problems falling asleep after doing sport, they should try to work out a little earlier.” KM
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